Oxidative dye compositions typically contain a coupler component and a primary intermediate. The coupler component and primary intermediate react in the presence of an oxidant to produce an oxidative dye which has utility in dyeing keratin fibers, such as hair. Typically the process is operated at pH 9-10.
Oxidative hair dyes suffer from certain disadvantages. They do not readily produce the brighter red and yellow colors that are currently fashionable. While such shades may be produced by adding yellow or red nitro dyes, these nitro dyes readily shampoo from hair and the brightness is soon lost, leaving the drabber oxidative color.
A further disadvantage of oxidative hair dyes is that when the process of oxidative hair dyeing is carried out at a low pH, dull drab dyeouts result. In view of the current move towards lower pH and less damaging products, this result is very undesirable.
In view of the above mentioned deficiencies, the value of a method for brightening shades afforded by oxidative dyeing is self-evident.
Solubilized vat dyes are brightly colored pigments, solubilized by reduction to the leuco state. In the leuco form, they are generally only weakly colored. Oxidation regenerates the bright color and insolubilizes the dye, thus making the color very resistant to removal by washing. Solubilized vat dyes are commonly used in the textile art to dye cellulosic fibers.